In the formation of integrated circuits, the components of the integrated circuit devices need to be patterned to form desirable shapes. A typical patterning process includes a photo lithography process, which includes coating a photo resist over a target layer that is to be patterned, light-exposing the photo resist using a lithography mask, developing the photo resist, and using the developed photo resist as an etching mask to etch the target layer. As a result, the layout of the developed photo resist is transferred to the underlying layer. The photo resist is then removed.
In some situations, after the photo resist is patterned, it may be found that the patterned photo resist has defects. The patterned photo resist is thus removed, and a new photo resist is applied and patterned again.